incubator-nuttx/binfmt/libelf/libelf_symbols.c

341 lines
9.6 KiB
C

/****************************************************************************
* binfmt/libelf/libelf_symbols.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/binfmt/elf.h>
#include <nuttx/symtab.h>
#include "libelf.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Constant Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: elf_symname
*
* Description:
* Get the symbol name in loadinfo->iobuffer[].
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
* EINVAL - There is something inconsistent in the symbol table (should
* only happen if the file is corrupted).
* ESRCH - Symbol has no name
*
****************************************************************************/
static int elf_symname(FAR struct elf_loadinfo_s *loadinfo,
FAR const Elf_Sym *sym)
{
off_t offset;
size_t bytesread = 0;
int ret;
/* Get the file offset to the string that is the name of the symbol. The
* st_name member holds an offset into the file's symbol string table.
*/
if (sym->st_name == 0)
{
bwarn("Symbol has no name\n");
return -ESRCH;
}
/* Allocate an I/O buffer. This buffer is used by elf_symname() to
* accumulate the variable length symbol name.
*/
ret = elf_allocbuffer(loadinfo);
if (ret < 0)
{
berr("elf_allocbuffer failed: %d\n", ret);
return ret;
}
offset = loadinfo->shdr[loadinfo->strtabidx].sh_offset + sym->st_name;
/* Loop until we get the entire symbol name into memory */
for (; ; )
{
FAR uint8_t *buffer = &loadinfo->iobuffer[bytesread];
size_t readlen = loadinfo->buflen - bytesread;
/* Get the number of bytes to read */
if (offset + readlen > loadinfo->filelen)
{
if (loadinfo->filelen <= offset)
{
berr("At end of file\n");
return -EINVAL;
}
readlen = loadinfo->filelen - offset;
}
/* Read that number of bytes into the array */
ret = elf_read(loadinfo, buffer, readlen, offset + bytesread);
if (ret < 0)
{
berr("elf_read failed: %d\n", ret);
return ret;
}
bytesread += readlen;
/* Did we read the NUL terminator? */
if (memchr(buffer, '\0', readlen) != NULL)
{
/* Yes, the buffer contains a NUL terminator. */
return OK;
}
/* No.. then we have to read more */
ret = elf_reallocbuffer(loadinfo, CONFIG_ELF_BUFFERINCR);
if (ret < 0)
{
berr("elf_reallocbuffer failed: %d\n", ret);
return ret;
}
}
/* We will not get here */
return OK;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: elf_findsymtab
*
* Description:
* Find the symbol table section.
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
int elf_findsymtab(FAR struct elf_loadinfo_s *loadinfo)
{
int i;
/* Find the symbol table section header and its associated string table */
for (i = 1; i < loadinfo->ehdr.e_shnum; i++)
{
if (loadinfo->shdr[i].sh_type == SHT_SYMTAB)
{
loadinfo->symtabidx = i;
loadinfo->strtabidx = loadinfo->shdr[i].sh_link;
break;
}
}
/* Verify that there is a symbol and string table */
if (loadinfo->symtabidx == 0)
{
berr("No symbols in ELF file\n");
return -EINVAL;
}
return OK;
}
/****************************************************************************
* Name: elf_readsym
*
* Description:
* Read the ELF symbol structure at the specified index into memory.
*
* Input Parameters:
* loadinfo - Load state information
* index - Symbol table index
* sym - Location to return the table entry
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
int elf_readsym(FAR struct elf_loadinfo_s *loadinfo, int index,
FAR Elf_Sym *sym)
{
FAR Elf_Shdr *symtab = &loadinfo->shdr[loadinfo->symtabidx];
off_t offset;
/* Verify that the symbol table index lies within symbol table */
if (index < 0 || index > (symtab->sh_size / sizeof(Elf_Sym)))
{
berr("Bad relocation symbol index: %d\n", index);
return -EINVAL;
}
/* Get the file offset to the symbol table entry */
offset = symtab->sh_offset + sizeof(Elf_Sym) * index;
/* And, finally, read the symbol table entry into memory */
return elf_read(loadinfo, (FAR uint8_t *)sym, sizeof(Elf_Sym), offset);
}
/****************************************************************************
* Name: elf_symvalue
*
* Description:
* Get the value of a symbol. The updated value of the symbol is returned
* in the st_value field of the symbol table entry.
*
* Input Parameters:
* loadinfo - Load state information
* sym - Symbol table entry (value might be undefined)
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
* EINVAL - There is something inconsistent in the symbol table (should
* only happen if the file is corrupted).
* ENOSYS - Symbol lies in common
* ESRCH - Symbol has no name
* ENOENT - Symbol undefined and not provided via a symbol table
*
****************************************************************************/
int elf_symvalue(FAR struct elf_loadinfo_s *loadinfo, FAR Elf_Sym *sym,
FAR const struct symtab_s *exports, int nexports)
{
FAR const struct symtab_s *symbol;
uintptr_t secbase;
int ret;
switch (sym->st_shndx)
{
case SHN_COMMON:
{
/* NuttX ELF modules should be compiled with -fno-common. */
berr("SHN_COMMON: Re-compile with -fno-common\n");
return -ENOSYS;
}
case SHN_ABS:
{
/* st_value already holds the correct value */
binfo("SHN_ABS: st_value=%08lx\n", (long)sym->st_value);
return OK;
}
case SHN_UNDEF:
{
/* Get the name of the undefined symbol */
ret = elf_symname(loadinfo, sym);
if (ret < 0)
{
/* There are a few relocations for a few architectures that do
* no depend upon a named symbol. We don't know if that is the
* case here, but return and special error to the caller to
* indicate the nameless symbol.
*/
bwarn("SHN_UNDEF: Failed to get symbol name: %d\n", ret);
return ret;
}
/* Check if the base code exports a symbol of this name */
symbol = symtab_findbyname(exports, (FAR char *)loadinfo->iobuffer,
nexports);
if (!symbol)
{
berr("SHN_UNDEF: Exported symbol \"%s\" not found\n",
loadinfo->iobuffer);
return -ENOENT;
}
/* Yes... add the exported symbol value to the ELF symbol table
* entry
*/
binfo("SHN_UNDEF: name=%s "
"%08" PRIxPTR "+%08" PRIxPTR "=%08" PRIxPTR "\n",
loadinfo->iobuffer, (uintptr_t)sym->st_value,
(uintptr_t)symbol->sym_value,
(uintptr_t)(sym->st_value + (uintptr_t)symbol->sym_value));
sym->st_value += (uintptr_t)symbol->sym_value;
}
break;
default:
{
secbase = loadinfo->shdr[sym->st_shndx].sh_addr;
binfo("Other: %08" PRIxPTR "+%08" PRIxPTR "=%08" PRIxPTR "\n",
(uintptr_t)sym->st_value, secbase,
(uintptr_t)(sym->st_value + secbase));
sym->st_value += secbase;
}
break;
}
return OK;
}